title: A vibrational circular dichroism approach to the determination of the absolute configurations of flavorous 5-substituted-2(5H)-furanones.
abstract: Sotolon (1) and maple furanone (2) are naturally occurring chiral furanones. These 5-substituted-2(5H)-furanones are industrially significant aroma compounds due to their characteristic organoleptic properties and extraordinarily low odor thresholds. Each enantiomer of 1 and 2 was successfully obtained by preparative enantioselective supercritical fluid chromatography. The absolute configuration of 1 was confirmed as (R)-(-)-1 and (S)-(+)-1 by adopting the vibrational circular dichroism (VCD) approach. The absolute configuration of 2, which has remained ambiguous since its discovery in 1957, was determined as (R)-(+)-2 and (S)-(-)-2 for the first time by the VCD technique. Surprisingly, the signs of the optical rotation of 2 are opposite of those of 1 regardless of their identical absolute configurations. This observation emphasizes the risk in absolute configurational assignments based on comparison of optical rotation signs of similar structures. Odor evaluation of the enantiomers of 2 revealed different odor intensities.
authors.affiliation: Faculty of Advanced Life Science, Frontier Research Center for the Post-Genome Science and Technology, Hokkaido University, Kita 21, Nishi11, Sapporo 001-0021, Japan.
authors.forename: Atsufumi
authors.initials: A
authors.lastname: Nakahashi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Yaguchi
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Miura
authors.forename: Makoto
authors.initials: M
authors.lastname: Emura
authors.forename: Kenji
authors.initials: K
authors.lastname: Monde
mesh_terms: D002942:Circular Dichroism / Q000379:methods*; D005663:Furans / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009812:Odorants / Q000032:analysis; D013237:Stereoisomerism
chemical_list: D005663:Furans